Substances From The Earth Part 2

Question 1

Can copper displace magnesium in a displacement reaction?

Answer 1

No, copper cannot displace magnesium because copper is less reactive than magnesium.

Question 2

What do you observe during a displacement reaction?

Answer 2

Look for a color change, a change in temperature, or the production of a metal deposit.
For example, in the magnesium and copper sulfate reaction, copper metal is deposited.

Question 3

How does a displacement reaction help determine the position of metals in the reactivity series?

Answer 3

Metals that can displace others are more reactive and placed higher in the reactivity series.
In the example, magnesium is higher than copper because it can displace copper from its compound.

Question 4

Which metals are extracted by electrolysis?

Answer 4

Metals above carbon in the reactivity series, such as aluminium, magnesium, calcium, and sodium, are extracted by electrolysis.

Question 5

Which metals are extracted by reduction with carbon?

Answer 5

Metals below carbon in the reactivity series, such as zine, iron, lead, and copper, are extracted by reduction using carbon or carbon monoxide.

Question 6

How is gold or platinum extracted?

Answer 6

Gold and platinum are unreactive and found in

their free state in nature, so they don’t require
extraction by electrolysis or reduction.

Question 7

Why is carbon used in the extraction of certain metals?

Answer 7

Carbon is used as a reducing agent because it can remove oxygen from metal oxides, thus extracting metals that are lower than carbon in the reactivity series.

Question 8

What are the main ingredients fed into the blast furnace for extracting iron?

Answer 8

The main ingredients are coke (carbon), limestone, and haematite (iron ore).

Question 9

What is the role of coke in the blast furnace?

Answer 9

Coke burns with oxygen to produce carbon dioxide (COz) and then reacts with carbon dioxide to form carbon monoxide (CO), which reduces the iron ore to iron.

Question 10

What are the key chemical reactions in the blast furnace?

Answer 10

• Step 1: Coke burns with oxygen to produce carbon dioxide.
• C(s) + 02(g) → CO,(g)
• Step 2: Carbon dioxide reacts with coke to form carbon monoxide.
• CO2(g) + C(s) → 2C0(g)
• Step 3: Carbon monoxide reduces iron (Ill) oxide (FezO3) to form iron.
• Fez03(s) + 3CO(g) → 2Fe(l) + 3COz(g)

Question 11

What happens to the impurities (such as silicon dioxide) in the ore?

Answer 11

The impurity silicon dioxide (SiOz) reacts with calcium oxide (CaO), formed by the decomposition of limestone, to form slag:
• CaO(s) + SiOz(s) → CaSiOs(I)

Question 12

How is slag removed from the furnace?

Answer 12

Slag floats on top of the molten iron and can be physically removed.

Question 13

What is the final product obtained at the bottom of the blast furnace?

Answer 13

Molten iron is collected at the bottom of the furnace, and it can be further processed.

Question 14

What are the typical properties of transition metals?

Answer 14

1. Different oxidation states (e.g., Iron can exist as Fe?* and Fei* in compounds).
2. Catalytic properties: They can act as catalysts in both their elemental and compound states.
3. Coloured compounds: Many transition metal compounds are colored.
4. High density: They tend to have relatively high densities.
5. High melting and boiling points: They generally have high melting and boiling points.

Question 15

What is rusting and how does it occur?

Answer 15

Rusting is a chemical reaction where iron reacts with oxygen and water to form a hydrated iron (Ill) oxide, commonly known as rust. The reaction requires both oxygen and water, and if either is absent, rusting will not occur.
Reaction:
4Fe(s) + 302(g) + 6H20(1) → 4Fe(OH)3(s)
Rust is an orange-red powder.

Question 16

What accelerates the rate of rusting?

Answer 16

Rusting is accelerated in the presence of salt, such as in saltwater, which speeds up the reaction between iron, oxygen, and water.

Question 17

What are the common methods for preventing rusting?

Answer 17

1. Painting: Often used for cars, ships, and bridges. If scratched, rust may spread under the paint.
2. Oil or Grease: Applied to moving parts of machinery to prevent rust and provide lubrication. Needs frequent renewal.
3. Plastic Coating: Used for items like garden furniture and fence netting. The plastic prevents contact with air and water, thus preventing rust.

Question 18

What happens if a plastic coating on iron is damaged?

Answer 18

If the plastic coating is cracked or broken, iron will rust because it will be exposed to air that contains both water vapour and oxygen, which are necessary for rusting to occur.

Question 19

What is electroplating and how does it prevent rusting ?

Answer 19

Electroplating involves coating metals like iron with a layer of tin (e.g., food cans) or chromium (e.g., faucets, bicycle parts). It provides both protection from rust and an attractive finish.
However, if scratched, the underlying iron may rust, especially if the electroplated metal is less reactive than iron, leading to rusting of iron in preference.

Question 20

What is sacrificial protection?

Answer 20

Magnesium and zinc are often used as sacrificial metals because they are more reactive than iron. In sacrificial protection, oxygen reacts with the more reactive metal (magnesium or zinc) instead of iron, protecting the iron from rusting.
This method is used on ship hulls with blocks of zinc or magnesium.

Question 21

What is galvanising and how does it prevent rusting?

Answer 21

Galvanising is the process of coating iron with zinc. It not only prevents oxygen and water from reaching the iron but also acts as a sacrificial metal.
Zinc reacts with oxygen before iron does, offering long-lasting protection, even in coastal areas.

Question 22

What are the environmental impacts of iron ore mining?

Answer 22

Iron ore mining causes:
1. Air pollution from combustion products like nitrogen oxides, carbon dioxide, carbon monoxide, and sulfur dioxide.
2. Water pollution from leaching metals and acidic water flowing downstream, affecting water bodies.
3. Land disturbance leading to loss of habitats and affecting wildlife, especially large mammals like bears and wolves.
4. Noise pollution from machinery, disturbing wildlife and communities.

Question 23

List uses of iron in everyday life.

Answer 23

• Hemoglobin in red blood cells (for oxygen and carbon dioxide transport)
• Cast iron (manhole covers, engine blocks)
• Wrought iron (ornamental work, gates)
• Catalyst in the Haber Process
• Steel production

Question 24

What are the properties of iron that make it versatile for use?

Answer 24

• Stronger than wood or copper
• Malleable (easy to shape when heated)
• Ferromagnetic (magnetic properties)

Question 25

State disadvantages of using iron.

Answer 25

• Rusts when exposed to air • Rusting is accelerated near the sea due to salt • Rusting increases cost (for protection)

Question 26

Describe the essential chemical reactions and conditions in the industrial extraction of aluminium.

Answer 26

• Bauxite treated with sodium hydroxide to remove impurities (iron (Ill) oxide, sand) • Aluminium oxide (alumina) obtained • Alumina dissolved in molten cryolite to reduce melting point • Electrolysis used to extract aluminium

Question 27

How is the extraction of aluminium a redox reaction?

Answer 27

• Aluminium oxide undergoes reduction (gain of electrons) at the cathode (aluminium is deposited). • Oxygen undergoes oxidation (loss of electrons) at the anode (oxygen gas is produced).

Question 28

What happens at the anode during the electrolysis of aluminium?

Answer 28

• The negatively charged oxide ions (02) are attracted to the anode. • They lose electrons (oxidation) to form oxygen gas. • Reaction: 202(1) → 02 (g) + 4e-

Question 29

What happens at the cathode during the electrolysis of aluminium?

Answer 29

• The positive aluminium ions (A|3*) are attracted to the cathode. • They gain electrons (reduction) to form molten aluminium. • Reaction: 4A|3* (I) + 12e* → 4AI (I)

Question 30

What happens to the oxygen produced during electrolysis and the graphite anodes?

Answer 30

• Oxygen reacts with graphite anodes, causing them to be oxidized to carbon dioxide. • Reaction: C (s) + 02 (g) → COz (g) • The anodes wear away and need regular replacement.

Question 31

What are the environmental impacts of mining bauxite?

Answer 31

• Requires heavy machinery and large-scale land disruption. • Mining can destroy habitats and affect local ecosystems. • Can be mitigated by land rehabilitation, recycling, and reducing consumption.

Question 32

List uses of aluminium in everyday life.

Answer 32

• Aircraft (as an alloy for strength and lightness) • Cooking utensils (light, good conductor of heat, resistant to chemicals) • Overhead electric cables (low density) • Aluminium paint (due to its appearance and resistance to corrosion)

Question 33

What are the best actions to take when considering the finite nature of many metals?

Answer 33

• Reduce: Minimize the amount of goods you buy and waste you produce. • Reuse: Use materials or items more than once to save energy and resources. • Recycle: Reprocess materials to create new products, reducing the need for new raw materials.

Question 34

What is a redox reaction?

Answer 34

• A redox reaction involves both oxidation and reduction, where one substance is oxidised and the other is reduced. • Oxidation is the gain of oxygen, while reduction is the loss of oxygen.